Fin end spacer for preventing merger of raised active regions

ABSTRACT

After formation of gate structures over semiconductor fins and prior to formation of raised active regions, a directional ion beam is employed to form a dielectric material portion on end walls of semiconductor fins that are perpendicular to the lengthwise direction of the semiconductor fins. The angle of the directional ion beam is selected to be with a vertical plane including the lengthwise direction of the semiconductor fins, thereby avoiding formation of the dielectric material portion on lengthwise sidewalls of the semiconductor fins. Selective epitaxy of semiconductor material is performed to grow raised active regions from sidewall surfaces of the semiconductor fins. Optionally, horizontal portions of the dielectric material portion may be removed prior to the selective epitaxy process. Further, the dielectric material portion may optionally be removed after the selective epitaxy process.

BACKGROUND

The present disclosure relates to a semiconductor structure, andparticularly to a method of preventing merger of raised active regionsfrom adjacent semiconductor fins employing a fin end spacer, andstructures formed by the same.

Fin field effect transistors are widely employed in advancedsemiconductor circuits for their superior performance over planar fieldeffect transistors. Fin field effect transistors provide a highon-current per area and full depletion of a channel during operation.One of the challenges for implementing fin field effect transistors isthe tendency for raised active regions, which include raised sourceregions and raised drain regions, in adjacent semiconductor fins to beelectrically shorted unless sufficient lateral distance is providedamong the adjacent semiconductor fins. While an electrical short betweentwo semiconductor fins may be avoided by increasing a lateral spacingbetween the two semiconductor fins, the increase in lateral spacingamong semiconductor fins results in an overall decrease in the arealdensity of semiconductor devices. Thus, a method is desired forpreventing electrical shorts among adjacent semiconductor fins withoutreduction in the areal density in the semiconductor devices.

SUMMARY

After formation of gate structures over semiconductor fins and prior toformation of raised active regions, a directional ion beam is employedto form a dielectric material portion on end walls of semiconductor finsthat are perpendicular to the lengthwise direction of the semiconductorfins. The angle of the directional ion beam is selected to be with avertical plane including the lengthwise direction of the semiconductorfins, thereby avoiding formation of the dielectric material portion onlengthwise sidewalls of the semiconductor fins. Selective epitaxy ofsemiconductor material is performed to grow raised active regions fromsidewall surfaces of the semiconductor fins. Optionally, horizontalportions of the dielectric material portion may be removed prior to theselective epitaxy process. Further, the dielectric material portion mayoptionally be removed after the selective epitaxy process.

According to an aspect of the present disclosure, a semiconductorstructure includes a fin active region located within a semiconductorfin that is located on a substrate. Surfaces of the fin active regioninclude a widthwise sidewall of the semiconductor fin and portions of apair of lengthwise sidewalls of the semiconductor fin. The semiconductorstructure further includes a dielectric material portion contacting anentirety of the widthwise sidewall, a raised active region including apair of doped semiconductor material portions located on the portions ofthe pair of lengthwise sidewalls, and a contact level dielectric layerin physical contact with the dielectric material portion and the raisedactive region.

According to another aspect of the present disclosure, a semiconductorstructure includes a fin active region located within a semiconductorfin that is located on a substrate. Surfaces of the fin active regioninclude a widthwise sidewall of the semiconductor fin and portions of apair of lengthwise sidewalls of the semiconductor fin. The semiconductorstructure further includes a gate structure straddling the semiconductorfin, a raised active region including a pair of doped semiconductormaterial portions located on the portions of the pair of lengthwisesidewalls and laterally spaced from the gate structure, and a contactlevel dielectric layer in physical contact with the widthwise sidewalland surfaces of the pair of lengthwise sidewalls of the semiconductorfin that are located between the gate structure and the raised activeregion.

According to yet another aspect of the present disclosure, a method offorming a semiconductor structure is provided. A semiconductor fin isformed on a substrate. The semiconductor fin includes a pair oflengthwise sidewalls and a widthwise sidewall. A dielectric materialportion is formed employing a directional ion beam that impinges on thewidthwise sidewall along a beam direction that is contained within avertical plane parallel to the pair of lengthwise sidewalls. At leastone raised active region is formed on physically exposed semiconductorsurfaces of the semiconductor fin while the dielectric material portionis present on the widthwise sidewall.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a top-down view of a first exemplary semiconductor structureafter formation of semiconductor fins and a shallow trench isolationlayer according to an embodiment of the present disclosure.

FIG. 1B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 1A.

FIG. 2A is a top-down view of a first exemplary semiconductor structureafter formation of gate structures according to an embodiment of thepresent disclosure.

FIG. 2B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 2A.

FIG. 2C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 2A.

FIG. 2D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 2A.

FIG. 3A is a top-down view of a first exemplary semiconductor structureafter formation of a dielectric material layer employing a directionalion beam according to an embodiment of the present disclosure.

FIG. 3B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 3A.

FIG. 3C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 3A.

FIG. 3D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 3A.

FIG. 3E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 3A.

FIG. 4A is a top-down view of a first exemplary semiconductor structureafter an anisotropic etch that removes horizontal portions of thedielectric material layer according to an embodiment of the presentdisclosure.

FIG. 4B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 4A.

FIG. 4C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 4A.

FIG. 4D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 4A.

FIG. 4E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 4A.

FIG. 5A is a top-down view of a first exemplary semiconductor structureafter formation of fin active regions according to an embodiment of thepresent disclosure.

FIG. 5B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 5A.

FIG. 5C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 5A.

FIG. 5D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 5A.

FIG. 5E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 5A.

FIG. 6A is a top-down view of a first exemplary semiconductor structureafter formation of raised active regions according to an embodiment ofthe present disclosure.

FIG. 6B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 6A.

FIG. 6C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 6A.

FIG. 6D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 6A.

FIG. 6E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 6A.

FIG. 7A is a top-down view of a first exemplary semiconductor structureafter formation of a contact level dielectric layer and various contactvia structures according to an embodiment of the present disclosure.

FIG. 7B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 7A.

FIG. 7C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 7A.

FIG. 7D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 7A.

FIG. 7E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 7A.

FIG. 8A is a top-down view of a second exemplary semiconductor structureafter formation of raised active regions according to an embodiment ofthe present disclosure.

FIG. 8B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 8A.

FIG. 8C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 8A.

FIG. 8D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 8A.

FIG. 8E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 8A.

FIG. 9A is a top-down view of the second exemplary semiconductorstructure after formation of a contact level dielectric layer andvarious contact via structures according to an embodiment of the presentdisclosure.

FIG. 9B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 9A.

FIG. 9C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 9A.

FIG. 9D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 9A.

FIG. 9E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 9A.

FIG. 10A is a top-down view of a third exemplary semiconductor structureafter removal of dielectric spacers according to an embodiment of thepresent disclosure.

FIG. 10B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 10A.

FIG. 10C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 10A.

FIG. 10D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 10A.

FIG. 10E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 10A.

FIG. 11A is a top-down view of the third exemplary semiconductorstructure after formation of a contact level dielectric layer andvarious contact via structures according to an embodiment of the presentdisclosure.

FIG. 11B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 11A.

FIG. 11C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 11A.

FIG. 11D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 11A.

FIG. 11E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 11A.

FIG. 12A is a top-down view of a fourth exemplary semiconductorstructure after formation of a contact level dielectric layer andvarious contact via structures according to an embodiment of the presentdisclosure.

FIG. 12B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 12A.

FIG. 12C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 12A.

FIG. 12D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 12A.

FIG. 12E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 12A.

FIG. 13A is a top-down view of a fifth exemplary semiconductor structureafter formation of a contact level dielectric layer and various contactvia structures according to an embodiment of the present disclosure.

FIG. 13B is a vertical cross-sectional view of the first exemplarystructure along the vertical plane B-B′ in FIG. 13A.

FIG. 13C is a vertical cross-sectional view of the first exemplarystructure along the vertical plane C-C′ in FIG. 13A.

FIG. 13D is a vertical cross-sectional view of the first exemplarystructure along the vertical plane D-D′ in FIG. 13A.

FIG. 13E is a vertical cross-sectional view of the first exemplarystructure along the vertical plane E-E′ in FIG. 13A.

FIG. 14 is a vertical cross-sectional view of a sixth exemplarystructure according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

As stated above, the present disclosure relates to a method ofpreventing merger of raised active regions from adjacent semiconductorfins employing a fin end spacer, and structures formed by the same.These aspects of the present disclosure are now described in detail withaccompanying figures. It is noted that like reference numerals refer tolike elements across different embodiments. The drawings are notnecessarily drawn to scale. As used herein, ordinals such as “first” and“second” are employed merely to distinguish similar elements, anddifferent ordinals may be employed to designate a same element in thespecification and/or claims.

Referring to FIGS. 1A and 1B, a first exemplary semiconductor structureaccording to an embodiment of the present disclosure can be formed byproviding a semiconductor substrate, which can be a bulk semiconductorsubstrate or a semiconductor-on-insulator (SOI) substrate. At least anupper portion of the semiconductor substrate includes a semiconductormaterial, which can be selected from elemental semiconductor materials(e.g., silicon, germanium, carbon, or alloys thereof), III-Vsemiconductor materials, or II-VI semiconductor materials. In oneembodiment, the semiconductor substrate can include a single crystallinesemiconductor material.

The upper portion of the semiconductor substrate can be patterned, by acombination of lithographic methods and an anisotropic etch, to form aplurality of semiconductor fins 30. For example, a photoresist layer(not shown) can be applied over the top surface of the semiconductorsubstrate and lithographically patterned to mask portions of thesemiconductor substrate in which the plurality of semiconductor fins 30is subsequently formed. The pattern in the photoresist layer can betransferred into the upper portion of the semiconductor substrate toform the plurality of semiconductor fins 30. If the semiconductorsubstrate is a bulk substrate, the remaining portion of thesemiconductor substrate underlying the plurality of semiconductor fins30 is herein referred to as a semiconductor material layer 10. In thiscase, the semiconductor material layer 10 is a substrate on which thesemiconductor fins 30 are formed. The semiconductor material layer 10functions as a substrate mechanically supporting the plurality ofsemiconductor fins 30. The plurality of semiconductor fins 30 and thesemiconductor material layer 10 collectively constitute a contiguoussemiconductor material portion. In one embodiment, the entirety of thecontiguous semiconductor material portion can be single crystalline.Alternatively, if the semiconductor substrate is asemiconductor-on-insulator substrate, a vertical stack of a buriedinsulator layer and a handle substrate layer can be present underneaththe plurality of semiconductor fins 30 in lieu of the semiconductormaterial layer 10. In this case, the vertical stack of the buriedinsulator layer and the handle substrate layer is a substrate on whichthe semiconductor fins 30 are formed.

The height of the semiconductor fins 30 can be from 5 nm to 1,000 nm,although lesser and greater heights can also be employed. The pluralityof semiconductor fins 30 and the semiconductor material layer 10 can bedoped with electrical dopants, i.e., p-type dopants or n-type dopants,or can be intrinsic. In one embodiment, the entirety of the plurality ofsemiconductor fins 30 and the semiconductor material layer 10 can have asame type of doping, which is herein referred to as a first conductivitytype. Optionally, a doped well (not shown) can be present in an upperportion of the semiconductor material layer 10 and underneath at leastone semiconductor fin 30. Optionally, a channel stop layer having adoping of the opposite conductivity type as an upper portion of at leastone semiconductor fin 30 may be provided at a bottom of the at least onesemiconductor fin 30 or a portion of the semiconductor material layer 10that underlies the at least one semiconductor fin 30. In general,various portions of the semiconductor material layer 10 and thesemiconductor fins 30 can be doped to provide suitable electricalisolation among the plurality of semiconductor fins 30.

As used herein, a “semiconductor fin” refers to a semiconductor materialportion having a pair of parallel vertical sidewalls that are laterallyspaced by a uniform dimension. In one embodiment, each semiconductor fincan have a rectangular horizontal cross-sectional area such that thespacing between the pair of parallel vertical sidewalls is the same asthe length of shorter sides of the shape of the rectangular horizontalcross-sectional area. As used herein, a “fin field effect transistor”refers to a field effect transistor in which at least a channel regionis located within a semiconductor fin.

Each semiconductor fin 30 is laterally bound by a pair of lengthwisesidewalls and a pair of widthwise sidewalls. As used herein, a“lengthwise direction” of an element refers to a direction that isparallel to the axis which passes through the center of mass of theelement and about which the moment of inertia of the element becomes aminimum. As used herein, a “lengthwise sidewall” of an element refers toa sidewall of an element that extends along the lengthwise direction ofthe element. As used herein, a “widthwise sidewall” of an element refersto a sidewall of the element that extends along a horizontal directionthat is perpendicular to the lengthwise direction of the element. In oneembodiment, each of the plurality of semiconductor fins 30 can have arectangular horizontal cross-sectional shape.

In one embodiment, lengthwise sidewalls of a semiconductor fin 30 can bewithin a pair of vertical planes laterally spaced from each other by thewidth w of the semiconductor fin 30. In one embodiment, the plurality ofsemiconductor fins 30 can be within a two-dimensional array having afirst pitch p1 along the lengthwise direction of the semiconductor fins30 and a second pitch p2 along the lengthwise direction of thesemiconductor fins 30. In one embodiment, widthwise sidewalls of a pairof semiconductor fins 30 laterally spaced along the lengthwise directioncan be laterally spaced from each other by a spacing s.

A shallow trench isolation layer 20 can be formed among the plurality ofsemiconductor fins 30. The shallow trench isolation layer 20 includes adielectric material such as silicon oxide. The shallow trench isolationlayer 20 can be formed by depositing a dielectric material over thesemiconductor fins 30 and the semiconductor material layer 10. Thedeposition of the dielectric material can be performed, for example, bychemical vapor deposition or spin coating. Excess portions of thedeposited dielectric material can be removed from above the top surfacesof the semiconductor fins 30, for example, by planarization (such aschemical mechanical planarization (CMP)). The shallow trench isolationlayer 30 laterally surrounds the plurality of semiconductor fins 30. Thetop surface of the shallow trench isolation layer 30 can be coplanarwith the top surfaces of the plurality of semiconductor fins 30.

Referring to FIGS. 2A-2D, a stack of gate level layers can be depositedand lithographically patterned to form gate structures (50, 52, 58). Thegate level layers can include, for example, a gate dielectric layer, aconductive material layer, and optionally, a gate cap layer.

The gate dielectric layer can be formed by conversion of surfaceportions of the semiconductor material of the semiconductor fins 30,deposition of a dielectric material, or a combination thereof. The gatedielectric layer can include a dielectric semiconductor-containingcompound (e.g., silicon oxide, silicon nitride, and/or siliconoxynitride) and/or a dielectric metal compound (e.g., dielectric metaloxide, dielectric metal nitride, and/or dielectric metal oxynitride).

The conductive material layer can include at least one conductivematerial such as a metallic material, a doped semiconductor material, ora combination thereof. The conductive material layer can optionallyinclude a work function metal layer that tunes the threshold voltage ofthe access transistor to be formed. The gate cap layer includes adielectric material such as silicon nitride or a dielectric nitride.

The gate level layers can be patterned by a combination of lithographyand etch to form the gate structures (50, 52, 58). The gate structures(50, 52, 58) straddle the portions of the semiconductor fins 30 thatbecome body regions of field effect transistors. Each remaining portionof the gate dielectric layer within a gate structure (50, 52, 58)constitutes a gate dielectric 50. Each remaining portion of theconductive material layer within a gate structure (50, 52, 58)constitutes a gate electrode 52. Each remaining portion of the gate caplayer within a gate structure (50, 52, 58) constitutes a gate capdielectric 58.

Portions of the semiconductor fins 30 that underlie the gate structures(50, 52, 58) correspond to the body regions of field effect transistorsto be subsequently formed for the trench capacitors (12, 42, 44). Thegate structures (50, 52, 58) can extend along the general direction ofthe widthwise direction of the plurality of semiconductor fins 30.

In one embodiment, the gate structures (50, 52, 58) are permanent gatestructures that are present in field effect transistors and function asa combination of a gate dielectric and a gate electrode. In oneembodiment, the gate structures (50, 52, 58) can be disposable gatestructures that are subsequently replaced with replacement gatestructures as known in the art.

Optionally, each gate structures (50, 52, 58) can further include adielectric gate spacer (not shown). The dielectric gate spacers can beformed by depositing a conformal dielectric layer and anisotropicallyetching the conformal dielectric layer. The conformal dielectric layercan include, for example, silicon nitride, silicon oxide, or siliconoxynitride. The etch process that removes horizontal portions of theconformal dielectric layer can be prolonged after horizontal portions ofthe conformal dielectric layer are removed so that vertical portions ofthe conformal dielectric layer on sidewalls of the semiconductor fins 30are removed, while the dielectric gate spacers remain on sidewalls ofthe gate electrodes 52. Each dielectric gate spacer, if present,laterally surrounds a gate electrode 52.

Referring to FIGS. 3A-3E, a dielectric material layer 56′ is formedemploying a directional ion beam. The directional ion beam can begenerated by a gas cluster ion beam implantation tool known in the art.The process of depositing or implanting a material employing thedirectional ion beam is herein referred to as a directional ion beamdeposition process. In one embodiment, the directional ion beamdeposition process can employ a gas cluster ion beam as known in theart. A gas cluster ion beam includes typically thousands of weakly boundatoms or molecules, which become ionized with a small amount ofelectrical charge that typically corresponds to the electrical charge ofa single electron or several electrons.

Angled gas cluster ion beam can be employed, which includes a dielectricmaterial or a cluster of a gas such as oxygen or nitrogen. In gascluster ion beam deposition, a cluster of ions having a molecular weightin a range from 100 to 100,000 can be singly ionized, or ionized with anumber of electrons that does not typically exceed 10. Such clusters ofions can travel at a low enough speed to be deposited on a surface ofthe target of the gas cluster ion beam, or to be implanted immediatelybeneath a surface of the target.

In one embodiment, the directional ion beam can include ionized clustersof a dielectric material, which is deposited on surfaces of thesemiconductor fins 30 that are not parallel to the lengthwise directionof the semiconductor fins 30 to form the dielectric material layer 56′.In this case, the dielectric material layer 56′ includes a depositeddielectric material that is formed by de-ionizing the ionized gasclusters in the gas cluster ion beam. For example, the directional ionbeam can include ions of a dielectric material such as silicon oxide,silicon nitride, silicon oxynitride, a dielectric metal oxide, adielectric metal nitride, or a combination thereof. The dielectricmaterial layer 56′ includes a deionized dielectric material that is thesame in composition as the dielectric material in the directional ionbeam except for the deionization of the dielectric material. In oneembodiment, the directional ion beam and the dielectric material layer56′ can include silicon oxide, silicon nitride, silicon oxynitride, adielectric metal oxide, a dielectric metal nitride, or a combinationthereof.

In another embodiment, the directional ion beam can include ionizedclusters of a gas such as oxygen or nitrogen, which is implanted throughsurfaces of the semiconductor fins 30 that are not parallel to thelengthwise direction of the semiconductor fins 30 to form the dielectricmaterial layer 56′. In this case, the dielectric material layer 56′includes a dielectric material that is formed by the combination of theimplanted ionized gas clusters in the gas cluster ion beam and thesemiconductor material in the semiconductor fins 30, and by deionizationof the combined material. For example, the directional ion beam caninclude ions of a cluster of oxygen atoms or ions of a cluster ofnitrogen atoms, and the dielectric material layer 56′ is formed byconversion of surface portions of the semiconductor fins 30 into adielectric material. The converted surface portions of the semiconductorfins 30 include surface portions of the semiconductor fins at thewidthwise sidewalls of the semiconductor fins 30 and at the top surfacesof the semiconductor fins 30. In one embodiment, the directional ionbeam can include oxygen and the dielectric material layer 56′ caninclude silicon oxide. In another embodiment, the directional ion beamcan include nitrogen and the dielectric material layer 56′ can includesilicon nitride.

In one embodiment, the directional ion beam can be angled relative tothe vertical direction perpendicular to the top surfaces of thesemiconductor fins 30 as illustrated in FIGS. 3A and 3B. In oneembodiment, the directional ion beam deposition process can be performedin two steps. In the first step, the direction of the directional ionbeam be selected that a first unit vector representing the direction ofthe directional ion beam includes a downward vertical component and ahorizontal component within the plane of the lengthwise direction of thesemiconductor fins 30. In the second step, the direction of thedirectional ion beam can be selected that a second unit vectorrepresenting the direction of the directional ion beam includes the samedownward vertical component as the first unit vector, and a horizontalcomponent that is the opposite of the horizontal component of the firstunit vector.

Thus, the first unit vector and the second unit vector are within avertical plane including the lengthwise direction of the semiconductorfins 30. Optionally, a third step in which the direction of thedirectional ion beam is along a downward vertical direction may be addedprior to the first step, between the first step and the second step, orafter the second step. Thus, the beam direction is contained within avertical plane parallel to lengthwise sidewalls of the semiconductorfins 30 throughout each step of the directional ion beam process. Allbeam directions during the directional ion beam process can be containedwithin a vertical plane parallel to the lengthwise sidewalls of thesemiconductor fins 30.

Methods of generating a gas cluster ion beam are known in the art, andcan be found, for example, in U.S. Patent Application Publication No.2002/0014407 to Allen et al. and U.S. Patent Application Publication No.2001/0010835 to Akizuki et al.

In one embodiment, the dielectric material layer 56′ can be a contiguousdielectric material layer that is formed on, and extends across, thewidthwise sidewalls and top surfaces of the semiconductor fins 30 andsidewall surfaces and the top surfaces of the gate stacks (50, 52, 58).The directional ion beam deposits, on the lengthwise sidewalls of thesemiconductor fins 30, no material, or lesser material than on thewidthwise sidewalls of the semiconductor fins 30.

In one embodiment, the directional ion beam deposits no material on thelengthwise sidewalls of the semiconductor fins 30. In this case, allportions of the lengthwise sidewalls of the semiconductor fins 30 thatare laterally spaced from the gate structures (50, 52, 58) by a greaterdistance than the thickness the dielectric material layer 56′ on thesidewalls of the gate structures (50, 52, 58), are physically exposedafter the directional ion beam deposition process.

In another embodiment, the directional ion beam deposits any material onthe lengthwise sidewalls of the semiconductor fins 30, for example, dueto a finite angular spread in the direction of the ion clusters. In thiscase, an isotropic etch such as a wet etch can be performed to removethe deposited material from the lengthwise sidewalls of thesemiconductor fins 30. All portions of the lengthwise sidewalls of thesemiconductor fins 30 that are laterally spaced from the gate structures(50, 52, 58) by a greater distance than the thickness the dielectricmaterial layer 56′ on the sidewalls of the gate structures (50, 52, 58),are physically exposed after the isotropic etch.

In one embodiment, the dielectric material layer 56′ can include siliconnitride or silicon oxide. The thickness of each dielectric materiallayer 56′, as measured at a widthwise sidewall of a semiconductor fin30, can be in a range from 3 nm to 30 nm, although lesser and greaterthicknesses can also be employed.

Referring to FIGS. 4A-4E, an anisotropic etch can be performed to removehorizontal portions of the dielectric material layer 56′. Remainingportions of the dielectric material layer 56′ includes dielectricmaterial portions 56 located on the widthwise sidewalls of thesemiconductor fins 30 and gate spacer 59 formed on the sidewall of thegate electrodes 52. Each dielectric material portion 56 can contact theentirety of a widthwise sidewall of a semiconductor fin 30. A pair ofgate spacers 59 contacts sidewalls of each gate structure (50, 52, 58)that straddles a semiconductor fin 30. The two gate spacers 59contacting the same gate structure (50, 52, 58) are disjoined from eachother, and are laterally spaced from each other by the lateral dimensionof the gate structure (50, 52, 58). As used herein, two elements aredisjoined from each other if there is no contiguous path that remainswithin, or on the surfaces of, the two elements and connects a pointwithin one of the two elements and another point in another of the twoelements. The gate spacers 59 can have the same composition as, and thesame thickness as, the dielectric material portions 56. Widthwisesidewalls of the gate structures (50, 52, 58) can be physically exposedto the ambient in which the first exemplary structure is present.

Referring to FIGS. 5A-5E, ion implantation is performed to introduceelectrical dopants into the semiconductor fins 30 (See FIGS. 4A-4D). Thegate structures (50, 52, 58) and the gate spacers 59 can be employed asan ion implantation mask. Optionally, an additional ion implantationmask (not shown), such as a patterned photoresist layer, may be employedas an ion implantation mask in addition to the gate structures (50, 52,58) and the gate spacers 59. If the semiconductor fins 30 includeelectrical dopants of a first conductivity type, ions of a secondconductivity type that is the opposite of the first conductivity typecan be implanted into unmasked portions of the semiconductor fins 30,i.e., portions that are not masked by an ion implantation mask. Forexample, the first conductivity type can be p-type and the secondconductivity type can be n-type, or vice versa.

A fin active region 3A is formed in each implanted portion of thesemiconductor fins 30. Each unimplanted portion of the semiconductorfins 30 constitutes a body region 3B. A p-n junction can be formed atthe interfaces between each adjoining pair of a body region 3B and a finactive region 3A.

As used herein, an “active region” can be a source region or a drainregion of a field effect transistor. As used herein, a “fin activeregion” refers to an active region located within a semiconductor fin.As used herein, a “fin source region” refers to a source region locatedwithin a semiconductor fin. As used herein, a “fin drain region” refersto a drain region located within a semiconductor fin.

Surfaces of each fin active region 3A can include a widthwise sidewallof the semiconductor fin (3A, 3B) and portions of a pair of lengthwisesidewalls of the semiconductor fin (3A, 3B). A dielectric materialportion 56 can contact the entirety of each widthwise sidewall of thesemiconductor fins (3A, 3B).

Optionally, dopants of the second conductivity type can be implantedinto the source regions 3S and the drain regions 3D of the semiconductorfins (3S, 3D, 3B) employing the combination of the gate structures (50,52, 58) and the gate spacers 59 as an implantation mask.

Referring to FIGS. 6A-6E, raised active regions 4A are formed onphysically exposed semiconductor surfaces of the semiconductor fins (3A,3B) by selective deposition of a semiconductor material. The selectivedeposition of the semiconductor material is performed while thedielectric material portions 56 are present on the widthwise sidewallsof the semiconductor fins (3A, 3B) and the gate spacers 59 are presenton sidewalls of the gate stacks (50, 52, 58) that extend along thewidthwise direction of the semiconductor fins (3A, 3B).

In one embodiment, the selective deposition of the semiconductormaterial can be performed by a selective epitaxy process. During theselective epitaxy process, the deposited semiconductor material growsfrom physically exposed semiconductor surfaces, i.e., the physicallyexposed portions of the lengthwise sidewalls and top surfaces of the finactive regions 3A, while the semiconductor material is not deposited on,and thus, does not grow from, dielectric surfaces such as the surfacesof the dielectric material portions 56, the gate spacers 59, and theshallow trench isolation layer 20.

A raised active region 4A can be formed directly on each fin activeregion 3A. As used herein, a “raised active region” refers to an activeregion (i.e., a source region or a drain region) that is located on, andoutside, a semiconductor fin or a preexisting semiconductor materialportion. In one embodiment, each portion of the raised active regions 4Acan be epitaxially aligned to an underlying fin active region 3A. Theraised active regions 4A can include the same semiconductor material as,or a semiconductor material different from, the semiconductor materialof the fin active regions 3A.

In one embodiment, each raised active region 4A can include a pair ofsemiconductor material portions contacting sidewalls of a fin activeregion 3A and another semiconductor material portion contacting a topsurface of the fin active region 3A. The pair of semiconductor materialportions contacting the sidewalls of the fin active region 3A is locatedon the portions of a pair of lengthwise sidewalls of a semiconductor fin(3A, 3B) that do not contact a gate dielectric 50 or gate spacers 59.The semiconductor material portion of the raised active region 4A thatis in contact with the top surface of the fin active region 3A laterallyextends from a top edge of a dielectric material portion 56 to a bottomedge of a gate spacer 59.

In one embodiment, the raised active regions 4A can be formed within-situ doping during the selective epitaxy process. Thus, each portionof the raised active regions 4A can be formed as doped semiconductormaterial portions. Alternatively, the raised active regions 4A can beformed as intrinsic semiconductor material portions and electricaldopants can be subsequently introduced into the raised active regions 4Ato convert the raised active regions 4A into doped semiconductormaterial portions.

In one embodiment, the various semiconductor material portions of theraised active regions 4A can be formed with crystallographic facets. Thecrystallographic facets of the raised active regions 4A can be at anon-zero, non-orthogonal, angle with respect to adjoining surfaces ofthe raised active regions 4A. In one embodiment, the various raisedactive regions 4A on different semiconductor fins (3A, 3B) can remaindisjoined from one another, i.e., not merged with one another.

Referring to FIGS. 7A-7E, a contact level dielectric layer 80 can beformed over the semiconductor fins (3A, 3B), the raised active regions4A, the gate structures (50, 52, 58), the dielectric material portions56, and the dielectric spacers 59. The contact level dielectric layer 80includes a dielectric material such as silicon oxide, silicon nitride,silicon oxynitride, porous or non-porous organosilicate glass (OSG), ora combination thereof. The contact level dielectric layer 80 can bedeposited, for example, by chemical vapor deposition. Optionally, thetop surface of the contact level dielectric layer 80 can be planarized,for example, by chemical mechanical planarization.

The contact level dielectric layer 80 is in physical contact with thedielectric material portions 56 and the raised active regions 4A. Thedielectric material of the contact level dielectric layer 80 can contactsidewalls of the gate stacks (50, 52, 58) that extend along thelengthwise direction of the semiconductor fins 30. In one embodiment,the dielectric material of the contact level dielectric layer 80 cancontact a sidewall surface of the gate electrodes 52 that extend alongthe lengthwise direction of the semiconductor fins 30.

Various contact via structures (8A, 8G) are formed through the contactlevel dielectric layer 80 to provide electrical contact to various nodesof the fin field effect transistors. For example, active region contactvia structures 8A provide electrical contact to the various raisedactive regions 4A and the fin active regions 3A, and gate contact viastructures 8G provide electrical contact to the gate electrodes 52.

The first exemplary semiconductor structure includes at least a finactive region 3A located within a semiconductor fin (3A, 3B) that islocated on a substrate 10. Surfaces of the fin active region 4A includea widthwise sidewall of the semiconductor fin (3A, 3B) and portions of apair of lengthwise sidewalls of the semiconductor fin (3A, 3B). Thefirst exemplary semiconductor structure includes a dielectric materialportion 56 contacting the entirety of the widthwise sidewall, and araised active region 4A including a pair of doped semiconductor materialportions located on the portions of the pair of lengthwise sidewalls.The entirety of the pair of lengthwise sidewalls of the semiconductorfin (3A, 3B) can be in physical contact with a gate dielectric 50, apair of gate spacers 59, or at least one raised active region includingthe raised active region 4A.

Referring to FIGS. 8A-8E, a second exemplary semiconductor structureaccording to an embodiment of the present disclosure can be derived fromthe first exemplary semiconductor structure of FIGS. 3A-3E by omittingthe processing steps of FIGS. 4A-4E and by performing the processingsteps of 5A-5E and 6A-6E. The dielectric material layer 56′ is acontiguous dielectric material portion that contacts the widthwisesidewalls and top surfaces of the semiconductor fins (3A, 3B), the topsurfaces of the gate stacks (50, 52, 58) and the sidewalls of the gatestacks (50, 52, 58) that extend along the widthwise direction of thesemiconductor fins (3A, 3B), and the top surface of the shallow trenchisolation layer 20. In one embodiment, openings in the dielectricmaterial layer 56′ may be present between a pair of semiconductor fins(3A, 3B) that are adjacent to each other along the lengthwise directionof the semiconductor fins (3A, 3B). In another embodiment, the entiretyof the top surface of the shallow trench isolation layer 20 can contactthe dielectric material layer 56′. Due to the presence of the dielectricmaterial layer 56′ on the top surface of the shallow trench isolationlayer 20, the bottommost surface of the raised active regions 4A may bevertically spaced from the top surface of the shallow trench isolationlayer 20 by the thickness of the dielectric material layer 56′.

Referring to FIGS. 9A-9E, the processing steps of FIGS. 7A-7E areperformed to form a contact level dielectric layer 80 and variouscontact via structures (8A, 8G). The second exemplary semiconductorstructure includes at least a fin active region 4A located within asemiconductor fin (3A, 3B) that is located on a substrate 10. Surfacesof the fin active region 3A include a widthwise sidewall of thesemiconductor fin (3A, 3B) and portions of a pair of lengthwisesidewalls of the semiconductor fin (3A, 3B). The second exemplarysemiconductor structure further includes a dielectric material layer56′, which is a dielectric material portion, contacting an entirety ofthe widthwise sidewall, a raised active region 4A including a pair ofdoped semiconductor material portions located on the portions of thepair of lengthwise sidewalls, and a contact level dielectric layer 80 inphysical contact with the dielectric material portion and the raisedactive region 4A. In one embodiment, the contact level dielectric layer80 can contact sidewalls of the gate stacks (50, 52, 58) that extendalong the lengthwise direction of the semiconductor fins (3A, 3B).

In one embodiment, the dielectric material portion of the dielectricmaterial layer 56′ contiguously extends over, and physically contacts, atop surface of the fin active region 3A. In one embodiment, the secondexemplary semiconductor structure can further include a gate electrode52 straddling the semiconductor fin (3A, 3B). The dielectric materiallayer 56′ can contiguously extend over the top surface of the gateelectrode 52.

Referring to FIGS. 10A-10E, a third exemplary semiconductor structureaccording to an embodiment of the present disclosure can be derived fromthe first exemplary semiconductor structure of FIGS. 6A-6E by removingthe dielectric material portions 56 and the gate spacers 59 selective tothe raised active regions 4A, the semiconductor fins (3A, 3B), and thegate structures (50, 52, 58). The selective removal of the dielectricmaterial portions 56 and the gate spacers 59 can be performed, forexample, by an isotropic etch such as a wet etch. For example, if thedielectric material portions 56 and the gate spacers 59 include siliconoxide, a wet etch employing hydrofluoric acid can be employed. If thedielectric material portions 56 and the gate spacers 59 include siliconnitride, a wet etch employing hot phosphoric acid can be employed.

Referring to FIGS. 11A-11E, the processing steps of FIGS. 7A-7E aresubsequently performed to form a contact level dielectric layer 80 andvarious contact via structures (8A, 8G). The third exemplarysemiconductor structure includes at least a fin active region 4A locatedwithin a semiconductor fin (3A, 3B) that is located on a substrate 10.Surfaces of the fin active region 3A include a widthwise sidewall of thesemiconductor fin (3A, 3B) and portions of a pair of lengthwisesidewalls of the semiconductor fin (3A, 3B). The third exemplarysemiconductor structure further includes a gate stack (50, 52, 58)straddling the semiconductor fin (3A, 3B), and a raised active region4A. The raised active region 4A includes a pair of doped semiconductormaterial portions located on the portions of the pair of lengthwisesidewalls and laterally spaced from the gate structure (50, 52, 58) by adistance that is the same as the thickness of the gate spacers 59 priorto removal. Additionally, the raised active region 4A includes anotherdoped semiconductor material portion in contact with a top surface ofthe fin active region 3A. In one embodiment, the entirety of the raisedactive region 4A, i.e., the combination of the pair of dopedsemiconductor material portions and the doped semiconductor materialportion overlying the fin active region 3A, can be laterally spaced fromthe gate stack (50, 52, 58) by a same lateral distance.

Further, the third exemplary semiconductor structure includes a contactlevel dielectric layer 80 in physical contact with the widthwisesidewall and surfaces of the pair of lengthwise sidewalls of thesemiconductor fin (3A, 3B) that are located between the gate structure(50, 52, 58) and the raised active region 4A. In one embodiment, thecontact level dielectric layer 80 can contact sidewalls of the gatestacks (50, 52, 58) that extend along the lengthwise direction of thesemiconductor fins (3A, 3B). In one embodiment, the contact leveldielectric layer 80 can be in physical contact with sidewalls of thegate electrode 52 within the gate stack (50, 52, 58).

Referring to FIGS. 12A-12E, a fourth exemplary semiconductor structureaccording to an embodiment of the present disclosure can be derived fromthe second exemplary semiconductor structure of FIGS. 8A-8E by removingthe dielectric material layer 56′ selective to the raised active regions4A, the semiconductor fins (3A, 3B), and the gate structures (50, 52,58). The selective removal of the dielectric material layer 56′ can beperformed, for example, by an isotropic etch such as a wet etch. Forexample, if the dielectric material layer 56′ includes silicon oxide, awet etch employing hydrofluoric acid can be employed. If the dielectricmaterial layer 56′ includes silicon nitride, a wet etch employing hotphosphoric acid can be employed.

Subsequently, the processing steps of FIGS. 7A-7E are performed to forma contact level dielectric layer 80 and various contact via structures(8A, 8G). The fourth exemplary semiconductor structure includes at leasta fin active region 4A located within a semiconductor fin (3A, 3B) thatis located on a substrate 10. Surfaces of the fin active region 3Ainclude a widthwise sidewall of the semiconductor fin (3A, 3B) andportions of a pair of lengthwise sidewalls of the semiconductor fin (3A,3B). The fourth exemplary semiconductor structure further includes agate stack (50, 52, 58) straddling the semiconductor fin (3A, 3B), and araised active region 4A. The raised active region 4A includes a pair ofdoped semiconductor material portions located on the portions of thepair of lengthwise sidewalls and laterally spaced from the gatestructure (50, 52, 58) by a distance that is the same as the thicknessof the gate spacers 59 prior to removal.

In one embodiment, the contact level dielectric layer 80 can contactsurfaces of the raised active region 4A, all surfaces of the lengthwisesidewalls of the semiconductor fin (3A, 3B) that do not contact the gatedielectric 50 or the raised active region 4A, and all widthwisesidewalls of the semiconductor fin (3A, 3B). In one embodiment, thecontact level dielectric layer 80 can contact sidewalls of the gatestacks (50, 52, 58) that extend along the lengthwise direction of thesemiconductor fins (3A, 3B). In one embodiment, the contact leveldielectric layer 80 can be in physical contact with sidewalls of thegate electrode 52 within the gate stack (50, 52, 58). In one embodiment,the entirety of the raised active region 4A, i.e., the pair of dopedsemiconductor material portions, can be laterally spaced from the gatestack (50, 52, 58) by a lateral distance, which is herein referred to asa lateral offset distance.

Referring to FIGS. 13A-13E, a fifth exemplary semiconductor structureaccording to an embodiment of the present disclosure can be derived fromthe first, second, third, or fourth exemplary semiconductor structure byadjusting the spacing between lengthwise sidewalls of semiconductor fins(3A, 3B) that neighbor each other along the widthwise direction of thesemiconductor fins (3A, 3B). During a selective deposition process thatforms the raised active regions 4A, various semiconductor materialportions that grow from different semiconductor fins (3A, 3B) can mergealong the widthwise direction of the semiconductor fins (3A, 3B) whilenot merging along the lengthwise direction of the semiconductor fins(3A, 3B) due to the presence of the dielectric material portion 56 (SeeFIGS. 6A-6E) or due to the presence of the dielectric material layer 56′(See FIGS. 8A-8E). Source regions in multiple semiconductor fins (3A,3B) and drain regions in multiple semiconductor fins (3A, 3B) can bemerged with one another to form a contiguous active region that contactmultiple semiconductor fins (3A, 3B) that are laterally spaced from oneanother along the widthwise direction of the semiconductor fins (3A,3B).

Referring to FIG. 14, a sixth exemplary semiconductor structureaccording to an embodiment of the present disclosure can be derived fromthe first, second, third, fourth, or fifth exemplary semiconductorstructure by substituting a semiconductor-on-insulator (SOI) substratefor a bulk semiconductor substrate. In this case, a vertical stack of aburied insulator layer 20′ and a handle substrate 10′ can be presentunderneath the semiconductor fins (3A, 3B).

The various exemplary structures of the present disclosure can beemployed to retard the growth of deposited semiconductor material duringthe selective deposition process that forms the raised active regions 4Aalong the lengthwise direction of the semiconductor fins (3A, 3B).Particularly, in combination with the facet formation on the surfaces ofthe raised active regions 4A, the presence of the dielectric materialportion 56 or the dielectric material layer 56′ (which is a contiguousdielectric material portion) prevents growth of the raised activeregions along the lengthwise direction of the semiconductor fins (3A,3B). Thus, electrical shorts between neighboring semiconductor fins (3A,3B) that are laterally separated along the lengthwise direction of thesemiconductor fins (3A, 3B) can be suppressed by the presence of thedielectric material portion 56 or the dielectric material layer 56′during the formation of the raised active regions 4A.

While the disclosure has been described in terms of specificembodiments, it is evident in view of the foregoing description thatnumerous alternatives, modifications and variations will be apparent tothose skilled in the art. Each of the embodiments described herein canbe implemented individually or in combination with any other embodimentunless expressly stated otherwise or clearly incompatible. Accordingly,the disclosure is intended to encompass all such alternatives,modifications and variations which fall within the scope and spirit ofthe disclosure and the following claims.

What is claimed is:
 1. A method of forming a semiconductor structurecomprising: forming a semiconductor fin on a substrate, saidsemiconductor fin including a pair of lengthwise sidewalls and awidthwise sidewall; forming a dielectric material portion in directphysical contact with said widthwise sidewall of said semiconductor finemploying a directional ion beam that impinges on said widthwisesidewall along a beam direction that is contained within a verticalplane parallel to said pair of lengthwise sidewalls; and forming atleast one raised active region on physically exposed semiconductorsurfaces of said semiconductor fin while said dielectric materialportion is present on said widthwise sidewall.
 2. The method of claim 1,wherein said directional ion beam includes ions of a dielectricmaterial, and said dielectric material portion includes a depositedportion of said dielectric material.
 3. The method of claim 1, whereinsaid directional ion beam includes ions of a cluster of oxygen atoms orions of a cluster of nitrogen atoms.
 4. The method of claim 3, whereinsaid dielectric material portion is formed by conversion of a surfaceportion of said semiconductor fin at said widthwise sidewall into adielectric material.
 5. The method of claim 1, further comprisingforming a gate structure across said semiconductor fin, wherein acontiguous dielectric material layer containing said dielectric materialportion is formed on a top surface of said semiconductor fin and a topsurface and a sidewall of said gate structure.
 6. The method of claim 5,further comprising removing horizontal portions of said contiguousdielectric material layer by an anisotropic etch, wherein a remainingportion of said contiguous dielectric material layer includes saiddielectric material portion and a gate spacer formed on said sidewall ofsaid gate structure.
 7. The method of claim 1, wherein said directionalion beam deposits, on said pair of lengthwise sidewalls, no material, orlesser amount of than on said widthwise sidewall.
 8. The method of claim1, wherein said forming said semiconductor fin comprises patterning anupper semiconductor material portion of a bulk semiconductor substrate.9. The method of claim 1, wherein said forming said semiconductor fincomprises patterning an upper semiconductor layer of asemiconductor-on-insulator substrate, and said substrate comprises atleast a buried insulating layer of said semiconductor-on-insulatorsubstrate.
 10. The method of claim 1, further comprising forming ashallow trench isolation layer at the footprint of said semiconductorfin.
 11. The method of claim 1, wherein said forming at least one raisedactive region comprises selective deposition of a semiconductormaterial.
 12. The method of claim 11, wherein said selective depositionis a selective epitaxy process, and said semiconductor material does notgrow from said dielectric material portion during said selective epitaxyprocess.
 13. The method of claim 11, wherein said semiconductor materialis a same semiconductor material as said semiconductor fin.
 14. Themethod of claim 11, wherein said semiconductor material is a differentsemiconductor material than said semiconductor fin.
 15. The method ofclaim 11, wherein said at least one raised active region containscrystallographic facets.
 16. The method of claim 1, further comprisingforming a contact level dielectric layer over said semiconductor fins,said dielectric material portion and said at least one raised activeregion.